Air blast circuit breaker and control therefor



DecQ4, 1945., w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21; 1940. a Sheets-Sheet 1 Dec. 4, 1945. w. M. SCOTT, JR J AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 2 Dec. 4, 1945. w. M. sco-r'r. JR 2,390,123

AIR BLAST CIRCUIT BREAKER AND CONTROL TIIERE'FOR Original Filed Dec. 21, 1940 8 Shets-Sheet 3 FlG.5

O I) .4, 1945. w. M. SCOTT, JR 2,390,128

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 4 1945. w. M. SCOTT, JR 2,390,128

AIR BLAST OIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 5 'FIGJO.

l 1 J46 77 ia w FIG. I W

. 4, 1945. w. M. SCOTT, Jr 2,390,123

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 6 Dec. 4, 1945. w. M; SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR 8 Sheets-Sheet 7 Original Filed Dec. 21, 1940 FIG. l3.

FIG. [4.

"' 4, 1945. w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21. 1940 8 Sheets-Sheet 8 Patented Dec. 4, 1945 AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR William M. Scott, Jr., Bryn Mawr, Pa., asslgnor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Original application December 21, 1940, Serial No. 371,092. Divided and this application February 28, 1942, Serial No. 432,774

38 Claims.

My invention relates in general to the field of circuit interrupters and more specifically concerns a circuit breaker and a control circuit therefor, particularly adaptable to the protection of mercury arc rectifiers and their associated circuits.

The anodes of a mercury arc rectifier are in general operated from the low voltage side of a multiphase transformer which, in turn, is usually fed from a three phase alternating current power supply. The number of anodes employed is dependent upon the particular installation, but in general the rectifier may contain 6, 12 or 24 anodes with the direct current load circuit joined between the neutral point of the transformer connection and the mercury pool cathode.

The protection of mercury arc rectifiers and their associated circuits concerns itself primarily with the instantaneous interruption offault currents which occur as a. result of back fires and other internal rectifier failures. The exact nature of back fires, internal short circuits and other electronic faults are not completely understood and the means for precluding the occurrence of such faults during rectifier operation have not been completely developed.

Upon the establishment of a back fire fault, current fiows between the unaffected anodes, the cathode and the back firing anode. The secondary of the transformer feeding the rectifier circuit is thus effectively short-circuited.

The magnitude of the current flowing in the circuit of the back firing anode may attain dangerously high values and the damage caused thereby may be extreme. This is particularly true in installations where several rectifiers are operating in parallel or where the rectifier direct current bus is connected to generative apparatus which can cause current to flow into the bus, as,

for example, a direct current shunt motor.

Under these circumstances, the direct current flowing from the cathode to the affected anode through the rectifier may cause the destruction of the anode or of the transformer-secondary.

Several methods may be utilized for controlling the fiow of current under the above noted circumstances. Thus the alternating current supply feeding the transformer primaries may be disconnected. This, however, still permits the flow of direct current from the cathode of the rectimit the flow of alternating current between the unaffeced anodes and the back firing anode.

Therefore, to effectively clear the circuit of the fault, it is necessary to have an extremely high speed circuit breaker operate instantaneously to disconnect the alternating current supply from the affected anode. This interrupts the fiow of both the alternating and direct current through the affected anode.

My invention contemplates a high speed single pole circuit breaker for connection in the anode lead of a mercury arc rectifier. The single pole circuit breakers required for all of the anodes are interlocked by a common switching and control system including a common source of actuating energy as, for instance, compressed air.

Upon the establishment of the back fire or similar fault, the rapid increase in current in the affected anode circuit operates instantaneously to trip the anode breaker and to initiate an air blast for extinguishing the are established therein. It is obvious that a single pole circuit breaker will operate upon the establishment of a fault to interrupt the affected circuit in less time than a mechanically interlocked multipole breaker.

Thus the single pole anode breaker which is in the affected circuit will operate with a minimum of time delay to interrupt the fault currents fiowing therein. My novel control system .interlocks all of the single pole circuit breakers by non-mechanical means, that is, the individual circuit breakers are interlocked by means of a plurality of compressed air manifolds and electrical circuits.

The instantaneous operation of a single anode breaker to remove a fault current will energize the tripping means of the anode breakers and thus the operation of a single breaker will cause a corresponding operation of all of the breakers.

However, the essential feature is the immediate operation of the circuit breaker in the anode circuit which may be carrying many times the rate current thereof, while the other anodes may not be carrying excessive currents.

It has been observed that if a back firing anode in a mercury arc rectifier is instantaneously disconnected and the current interrupted and then immediately reinserted into the circuit, normal operating conditions'frequently may be restored. Therefore, in mercury arc rectiiier installations, in order to avoid a cbmpleteshut down of the operating equipment upon the occurrence of an anode circuit fault, there is therefore provided an interlocking system in which the automatically tripped circuit breaker does not affect the circuit breakers in the unaffected anode leads.

Upon the complete interruption of current flow in the affected anode, th circuit breaker in the affected anode lead is reclosed. If operation in this manner restores normal conditions, then the direct current load will be maintained with but relatively small ripple in the line voltage for the duration of the temporary back fire. This is exdue to mercury arc rectifier back fires may inconvem'ence the users of the direct rectified current.

However, it is quite possible that the fault may not be one of a temporary nature, that is, instantaneous interruption and reconnection may not operate to remove the faulty condition and of course, the ailected circuit breaker will continuously operate to open and reclose the circuit breaker contacts.

Therefore, a counting or time delay device may be included in the control system for the individual anode poles and may be interlocked with the control systems of the other circuit breaker poles so that after a circuit breaker pole has opened a predetermined number of times due to a faulty anode condition, the device willactuate the interlocking tripping mechanism to isolate all of the anodes from the multi-phase transformer and effectively isolate the mercury arc rectifier. Should the fault condition cease to exist before the affected anode circuit breaker had opened and re-closed its predetermined number of times, the other poles would remain closed and the counting device would automatically reset for a future operation. The control system also includes a means for indicating the number of automatic operations in each circuitbreaker in order that faulty operation of any one anode may be readily determined 8,390,128 tremely desirable ininstances whereshut downs rectifier operation and which will isolate the mercury arc rectifier if a permanent fault has occurred therein.

It is still a further object of my invention to interlock the plurality of single pole anode circuit breakers by means of a compressed air opening and reclosing system and a plurality of electrical switching devices for operating the same.

These and other objects will become apparent from the following specification taken in connec-- tion with the accompanying drawings, in which:

Figure 1 is a broken cross-sectional view'of a single pole circuit breaker and the means for interlocking the same with a plurality of similar poles.

Figure 1a is an enlarged view of part of the circuit breaker shown in Figure 1.

Figure 2 is a fragmentary view of one of the control switches operable by the circuit breaker taken along the line 2--2 of Figure 1. t

Figure 3 is-a cross-sectional view of a single pole circuit breaker taken along the line 3-1 of Flgurel. t

Figure 4 is a fragmentary cross-sectional view of the over-load magnet and adjusting'means therefor taken alongthe line (-1 of Figure 1.

and resettable means are included for indicating which of the poles last'operated.

- The high speed circuit breaker which I have devised comprises a pair of cooperable contacts upon which a directed high velocity air blast may operate to cause contact disengagement and are extinction with a minimum of time delay.

A diaphragm valve in each of the anode circult breakers is the air blast control element and all of these valves are .interlocked by means of a manifold in a manner such that automatic tripping of a single pole or manual tripping of all poles may be obtained. The interlocked diaphragm valves serve, in addition, to protect the main air storage tank so that the entire charge of air contained therein will not be lost during Figure 5 is a broken cross-sectional view of the circuit breaker tripping manifold takenalong the line 5-5 of Figure 1;

Figure 6 is an enlarged cross-sectional view of the check valve operable within the air manifold taken along the line Bl of Figure 5.

Figure 7 is a supplementary view of the check valve taken along the line 1-1 of Figure 6.

Figure 8 is a cross-sectional view of the single pole circuit breaker indicating the involute air passage surrounding the circuit breaker contacts taken along the line 8-8 of Figure 1.

Figure .9 is an end sectional view of the circuit breaker taken along the line 0-9 of Figure 1.

Figure 10 is an end cross sectional view of the circuit breaker taken along the line Ill-i0 of Figure 1.

Figure 11 is a fragmentary cross-sectional view taken alongline ll ll of Figure'10. t

Figure 12 is a schematic representation of the plurality of anode circuit breakers and the control means therefor.

Figure 13 is a schematic representation of one Figure 14 is a fragmentary schematic view of a trol.

It is therefore an object of my invention to provide a high speed single pole circuit breaker,

particularly adapted for operation in the anode lead of a mercury arc rectifier.

Another object of my invention is to provide means for effectivel interlocking a plurality of single pole circuit breakers.

Still another object of my invention is to provide a plurality of circuit interrupters which are effectively interlocked; which interlocking permits independent operation of a single pole when required by the circuit.

A still further object of my invention is to provide a circuit interrupter which operates to interrupt single anode faults without necessarily disconnecting .the' entire rectifier from the cir-.

' Figurelfi is a schematic representation of a six-phase mercury arc rectifier andthe corresponding number of single pole circuit breakers in the anode leads thereof.

Figure 16 is a fragmentary schematic view of the over current magnet and illustrates one form of polarizing coil for reverse current tripping.

In Figure 1 there is shown a single pole circuit breaker which is one element of a plurality of interconnected poles operable within the anode leads of a mercury arc rectifier. Figure 15 schematically indicates a typical installation which in this instance includes a six-phase mercury arc.

rectifier employing in each of the anode leads, a

circuit breaker element of the type indicated in modification or the controlling system of Figure ondary is connected to the negative terminal of the direct current transmission line and the mercury pool cathode 24 is the positive terminal thereof.

The six anodes" within the mercury arc rectifier are each joined to a corresponding anode lead from the six-phase secondary and a single pole circuit breaker is inserted in each of these leads, as will hereinafter be indicated. The plurality of circuit breaker elements employed are interconnected to effect the desired circuit interruptions for mercury arc rectifier operation. In Figure there is shown a typical backfiring condition. Current from each of the five normal anodes flows through the faulty anode 25' and results in a heavily overloaded anode circuit. In addition to the sum of all the alternating current components, a direct current, which is schematically indicated by the feathered arrow, flows through the affected anode. This component may be exceptionally great if the direct current circuit comprises generative apparatus.

If, for instance, the direct current load comprises a shunt motor 26, as is schematically illustrated, or additional mercury arc rectifiers in parallel, or a parallel direct current generator,

the direct current will be the result of the current which this apparatus may supply through the low impedance transformer secondary and the relatively low impedance are from the oathode to anode 25'. This component of the fault may therefore be particularly destructive to the anode and the corresponding transformer secondary.

As has hereinabove been pointed out, a cathode protective breaker 21 which is in series with the direct current transmission line may be tripped to remove the direct current component that flows through the faulty anode. This, however, will not preclude the flowof excessive alternating currents therein.

A current interrupter in the anode circuit of the rectifier will operate to remove both alternating and direct currents and isolate the recti fier. But since a single anode is particularly overloaded, an independently operating single pole circuit breaker will best be suited to relieve the fault condition with a minimum of time delay. This individual breaker may be caused, during interruption, to actuate the tripping mechanisms of all other anode breakers to result in the ultimate isolation of the rectifier.

The exact nature of the single pole circuit breaker and of the tripping and control means therefor will now be described and reference is now made to the cross sectional view of the single pole breaker, Figures 1 and 1a.

The single pole of the circuit breaker illustrated consists essentially of two cooperable contacts 3| and 32, and means for directing and controlling an air blast which enters through the pipe 33 and passes over the separated contacts during circuit interruption. The plurality of circuit breakers which are required for the various rectifier anode leads may all be mounted directly upon a common storage tank to shorten and thus facilitate piping connections thereto as indicated schematically in Figure 12. That is, the base 34 of the flange 35 may be coupled by bolts or other suitable means directly to an air storage tank which is charged by means of a compressor. The

systems maybe adjusted so that pressure therein remains within predetermined limits and that any variations of pressure outside of these limits may operate to open the circuit breakers.

The main metallic casting 35 of the circuit breaker is, as will hereinafter be shown, at a relatively high potential and it is therefore necessary to electrically isolate the casting from ground potential. Therefore, the casting 35 is supported upon the air storage tank by'means of a pipe 33 made of a suitable insulating material and of suilicient length to ensure a minimum of leakage and to preclude the possibility of an arc between the circuit breaker frame and the air storage tank.

The base of the casting 35 is preferably a, circular external flange 31 which is supported upon the pipe 33 and thus upon the air storage tank by means of the piping flange 4| which is in screw thread engagement at 42 with the insulating pipe 33. The external flange 31 of the casting 35 may then be fastened to the piping flange by any convenient means, as for instance, a plurality of machine screws, but first an annular asket 43 is inserted therebetwe en to preclude the leakage of air at the junction of the surfaces. I

A tapered opening 44 of diameter equal to the inner diameter of the insulating pipe 33 admits to the casting 36 air which is then conducted through the cored passage 45 to the controllable diaphragm valve 45.

The cored passage 45 terminates in an annular air passage 41 which completely surrounds the diaphragm valve 45. Aligned with the valve is a projecting circular pipe 5| which provides a pa"- sage 52 for directing the incoming air to the contacts 3| and 32.

The end surface 53 of the inwardly projecting pipe 5| is smoothed to cooperate with a layer 54 of valve seat material which is carried by the valve diaphragm 45.

The passage 52 provided by the annular metallic projection 5| which has been integrally molded into the casting 36 is more clearly illustrated in Figures 3 and 8 wherein it may be seen that the passage 52 is a cored involute, spiralling to completely surround the contact 3| as indicated in Figures 1 and 3.

Thus, air entering into the passage 52 will be conducted to the contact 3| and the air stream will completely surround the contact. 7

Returning now to the air control means, that is, the diaphragm valve 45 illustrated in Figure 1, it may be seen that air flow in the cored passage 52 is controlled by the position of the valve seat material 54 relative -to the edge 53 of the inwardly projecting'pipe 5| The valve diaphragm is supported upon the metallic casting 35 in a counter-bored recess 55 in the wall of the casting.- The'diaphragm 46 is a circular piece of flexible material such as rubber and is held in the counterbore 55 by means of a circular dome shaped member 56 which is turned down at 51 to correspond with the inne diameter of the counter bore 55.

The dome shaped member 55 is then securely fastened to the main casting 35 by means of a plurality of machine screws 5| which are circularly disposed as is more clear-1y indicated in the rear view (Figure 5) of the dome shaped member 55.

The machine screws 5| pass through a corresponding set of perforations 52 in the dome shaped member and engage threaded perforations 53 within the main casting-36. The valve diaphragm 45 is thus securely clamped between the projection 51 and the main casting 36. In order to assure 'an air tight joint at this point and to prevent radial movement of the edge of the diaphragm when subjected to air pressure, a wedge shaped circular protrusion 34 on the projection 31 is forced into the resilient material of the diaphragm when the screws 3| are tightened.

The member 33 has been machined to provide the spherical dome 33 and thus axial displacements of the diaphragm 43' are limited to the space between the dome 33 and theend 33 of the inwardly projecting cored pipe 3|. The valve diaphragm 43 is of flexible material and has secured to it two circular metallic disks 33 and 31 on either side of the flexible material. The face of'disk 31 is faced with a valve seat material 34 which will provide a suitably closed surface engagement with the end 53 of the inwardly pro- :Iecting, passage. The four layers of material therefore which comprise the movable portion of the valve are bound together by the screw II and its associated nut I2 which bears against a conical shaped metallic member 13 which assists in directing the now ofair toward the discharge when the valve is open. I

The rear face I4 of the metallic disk 33 has been machined to correspond with the dome shaped chamber 33. Thus it may be seen that the inflowing air which enters through the insulating pipe 33 is guided to the annular cored passage 41 surrounding the inwardly projecting pipe ll and the face-of the diaphragm valve. If now the diaphragm 43 is displaced to the left, as viewed in Figure 1, the air will. as indicated by the arrow I heads of Figure 1 enter from the passage 43 and passage 4! into the tapered and spiralled passage 52 which supplies air to the contact engaging surfaces. Therefore, actuation of the diaphragm valve 43 will control the circuit breaker blast and will be discussed in greater detail in later paragraphs inasmuch as the structural details of the circuit breaker will now be described.

Contact 3| is a conically shaped butt contact engageable with a nozzle shaped contact 32 along the contact surfaces 3 I and 32' which have been non-welding alloy of tungsten and silver, silver and graphite, or the like. v

Nozzle shaped contact 32 is flxed relative to the main frame 33 of the circuit breaker whereas contact3I is slidable relative thereto. As indicated in Figures 1 and 3, contact 3I has been displaced from its closed position and thus the air flow is indicated by the arrow heads. As the faced with a suitable contact material such as a blast air approaches the contacts throughv a Nozzle shaped contact 32 is supported withinv a circular opening I5 which is formed within a projecting extension 13 of the 'main casting 33.

As will be pointed out in later paragraphs, the mainframe 33 is at the potential of contact 3| and therefore it is necessary to support contact 32 within the opening I5 by suitable means of insulating material. Contact 32 is secured between the line terminal 11 and the exhaustpipe and muflier 3|, and 32.. This assembly is made rigid by an external flange 33 on the outer end of con- This action will facilitatetact 32 nesting within counterbores 34in ternii-- nals II and 33 in exhaust pipe 3| so that when the parts are assembled as indicated in Figures 1 and 3, the. contact 32 will be rigidly held therebetween. I v

a The entire assembly is maintained in fixed relation by means of a plurality of studs 33 extending from terminal I1 and passing through correspondin'g perforations 31 within the flange end of the exhaustpipe 3|. This is more clearly indicated in Figure l0 .where the approximately square flanged end of the exhaust pipe II is illustrated as carrying in the corners thereof the plurality of nuts 3 I which as in Figures 1 and 3 serve to clampthe exhaust pipe to the termin 11 which is also-indicated in Figure 10.

The assembly of contact 32, terminal I1 and exhaust pipe lIis-then clamped-to the main casting 33 by meanspf a plurali y of socket head screws 32 more clearly indica d in Figures 10 and 11. That is, line terminal 11 provides a series of perforations 33 through which the socket head screws 32 may pass into a corresponding tapped perforation 34 in the main casting 33.

It has been previously pointed out that it is essential to insulate line terminal 11 from the main frame 33 inasmuch as frame 33 is at the potential of contact 3| and line terminal 11 is at the potential of contact-32. Therefore, the socket head screws 32 have been sheathed in insulation. that is, a cylindrical tube of insulation 33 has been provided to prevent the shank of the bolt from contacting terminal 11 andthe head of the bolt has been similarly protected by a cylindrical cup 33 which has been perforated at 31 to allow the passage of the insulating tube 35.

It should be noted that if desirable, the various tubes of insulating material may be dispensed with if the socket head screws or other types of screws employed to bind the assembly of contact 32, terminal 11 and exhaust pipe 0| to the main frame 33 are made of a sufficiently strong insulating material.

Prior to the insertion of bolts 32 into the main frame 33, a-plate III of insulating material is placed therebetween and is perforated at I02 in order to correspond with all of the insulating sheaths 33 which cover the socket head screws employed in the embodiment illustrated.

To serve as additional insulation between the frame 33 and the lineterminal 11, a cylindrical tube I03 is cemented to the insulating plate IOI at perforation I04 and is of an outside diameter equal to the inner diameter of the passage "I5 in the main frame 33. Therefore, when the contact 32 is secured by means of flange 33 between the line terminal 11 and the exhaust pipe an and v this entire assembly is subsequently clamped to the mainframe as indicated in Figure 1, along with the insulating plate IM and the insulating cylinder I03, contact 32 will project into the passage I3 and will be centrally located with respect to the spirally oriented air passage 32.\

It should be noted that the outer cylindrical" a .whichis at the potential of line terminal 11. This,

in effect, provides an increased leakage path and therefore reduces the possibility of electrical break-down atthis point.

The nozzle shaped passage III] of the contact 32 provides for the expansion of the blast air in order to reduce back pressure.

Exhaust pipe 31 juxtaposed against contact 32 along the face III provides a tapering passage which is a continuation of the tapering passage of the low pressure side of the nozzle. Th pipe supports, by means of the screw threads II2, the hollow cylindrical mumer 82 and the deionizing stack III. This stack comprises a plurality of parallel metal laminations over which the hot are products pass and are effectively cooled.

Conical contact 3| is mounted upon a piston II4 which is slidable within a cylinder I I5 in the main casting 36. In order to prevent leakage of air over the piston II4, a series of grooves II6 have been turned in the piston and piston rings or other packing may be inserted therein.

The contact 3| is centered on the piston II4 by a boss extending into a perforation I I1 and is clamped thereto by means of the screw threaded plunger rod I2I. This rod has been turned down and threaded at the end I22 which engages a tapped perforation in the contact 3i. By tightening these threads, the annular flange I23 is brought into contact with a flexible conductor I24 which has been perforated at I25 to allow the passage of the plunger rod I2I. Therefore, bringing plunger rod I2I into screw thread engagement with the perforation in 3i will securely clamp the assembly of contact 3|, piston I I4, and flexible conductor I24.

The movement of piston H4 is limited by the engagement of contact faces 3| and 32' at one end of the stroke (at which time the circuit is closed) to the engagement of the rear face of the piston with a ring shaped rubber or other flexible washer I26 which has been secured within a reentrant flange I21, molded into the main casting 36. As indicated in Figure 3, the outer edge of this flange has been cut away at I3I to allow for the passage of the flexible conductor I54.

Piston II4 therefore which is operable within the chamber II5 between the limits of engagement with the stationary contact and the annular rubber ring I26, is the operating element of the circuit breaker, that is. operation of the piston H4 in either direction by means of air pressure controlled by diaphragm valve 46- or any of the other valves which will hereinafter be discussed, will operate either to open or close the circuit.

Contact 3I is connected to the circuit through the flexible conductor I2 1 which allows movement without in any way impeding movementof the piston. The flexible conductor I24 is composed of a series of highly conductive metal laminations stacked together by suitable means and is fastened at either end to a bifurcated member by means of the plurali't" of machined screws I32. The bifurcated member I33 then continues downward to engage the line terminal I34 and the cable I35 from the external circuit bysmeans of the bolt or other fastening means I3 Supported by the flange I21 is a member I which positions th plunger rod I2I. The memher I contains a cylinder I42 in which is operable a piston I43 and its associated packin I44 mounted on the end of the plunger.

Secured in one end of the cylinder I42 is a flanged bushing I6I which in this embodiment is fastened by the screw thread I52. A perforation I53 allows the passage of the plunger rod I 2I but this perforation is within a reentrant flange I54 for reasons which will be pointed out in a following paragraph.

A flange I56 on the plunger rod I2I which originally had been machined circular similar to the flange I23 is milled oil. so that it may engage the rectangular cross section of a U-snaped channel I56 as indicated In Figures 1 and 3.

The piston I43 is drilled at. I51 to allow the passage or plunger rod I2I which is then clamped thereto by means of the nut I6I. Prior to the application of the nut, however, a series of fiber or other type of washers I44 are slipped over the plunger rod Ill and this when clamped by nut I6l provide the necessary air tight packing for piston I43. The U-shaped channel I56 is held between the flange Ice and the piston I43 and is allowed to extendout through the axial perforation Io'2 in member I4I so that it may cooperate with the switching member Hi3 which will hereinarter be described.

Contact 3| 1S blased normally towards the open position, that is, the position corresponding to contact between the rear of the piston In and the shock absorbing member I26. This is accomplished by means of a compression spring I64 which is lodged between the reehtrant nange I54 previously described and the ilange I55 which supports the U-shaped channel. As the spring is normally under compression, and as the reentrant nange I04 is nxed, there is a tendency to draw contact 3| from engagement with contact 32.

The outer end of the closing cylinder casting is provided, at its loweredge with a pair of horizontal lugs I69. 'lhe bifurcated member I33, which is also the over-current bus bar, is supported against the bottom of these lugs by studs threaded into the bar, passing through holes in the lugs and held in position by nuts and lock washers Ill]. The lower end of the bar is braced by the member I83 as will be described in a following paragraph.

The forked conductor I33 supports, upon a protrusion, the plurality of machine screws Ill which pass through magnet lamihations I12. The magnet is composed of stacked soft iron or other magnetic laminations each of which is horse-shoe shaped and as such surrounds the magnet bus bar I13 ksee Figure which is an integral extension. of the forked member I33. As it is desirable to preclude the possibility of current flow-- ing through the magnet, the screws I1I are insulated by means of insulating sheaths I15 which completely surround their respective screws.

Referring now to Figure 4, which is a cross sectional view of the magnet and magnet bus bar I13, it may be seen that the magnet bus passes directly through the horse-shoe shaped magnet formed by the stacked laminations. The armature I16 of this magnet is a trapezoidal laminated bar of magnetic material which is carried upon a plunger I11.

The operation of the magnet may be briefly explained by noting that the line current will flow through the bus bar indicated in Figure 4, and will establish a cylindrical magnetic field surrounding the conductor itself. Therefore, the stacked laminations comprise a magnetic circuit for the flux in the vicinity thereof and accordingly the faces I8I and I82 act as magnet poles and exert a force of attraction upon the wedge shaped armature I16.

It is frequently desirable particularly in the protection of the anodes of mercury arc rectiflers to cause circuit interruption upon the flow of small reverse currents. This may be accomplished by means of a polarizing coil upon the magnetic structure as is illustrated in the simplest possible form in Figure 16. I

Here a coil or plurality of coils I surrounding th magnetic structure is continuously energized by a constant voltage. The force exerted upon armature I16 due to the flux of this polarizing coil is in the same sense as the. force which will be exerted by the flux-produced as a result of reverse current flowing through bus bar I13.

The polarizing flux alone is insufllcient to cause displacement of armature I13, but may be adjusted so that relatively small reverse currents will result in actuation thereof to open the circult breaker. The applicationof a polarizing coil does not prevent normal operation of magnet upon forward currents.

As indicated in Figure 1, the magnet bus I13 which may, during short circuit periods carry considerable currents, is braced so as to preclude any mechanical deformation thereof due to the stresses developed by virtue of the magnetic forces. The brace comprises the metallic member I83 which has been fastened by means of machine screws I84 to the frame of casing 36 and by means of the plurality of machine screwsand bolts I85 to the magnet bus. This brace is insulated from the flange 31 by insulating layer I89; however, the brace itself may be formed from an insulating material.

The electromagnetic device I12 in conjunction with the armature I16 controls the diaphragm valve 46 to control the admission of air to the contact chamber. The plunger rod I11 operates under the influence of the magnet I12 and in order that the rod I11 be maintained in alignment, it passes through a perforation I86 within the magnet lamination stack and through a perforation I31 in the magnet bus bar I13.

The armature I16 is clamped securelyto the rod I11 between the flange I19 and nut I9I which engages a series of screw threads on rod I11. The rod I11 is continuously biased towards the right as viewed in Figures 1 and 4, by means included within the cylindrical member I93.

The cylindrical member I93 is fastened to the main frame 36 through the dome shaped member 66 by means of the screw threads I94 upon both the cylindrical member and a corresponding hollow in the rear of the dome shaped member.

However, inserted into the hollow of the dome sh ped member prior to the insertion of the hollow cylindrical member I93, is a small circular metalpiece I95 which contains a conical valve seat I96 and a cylindrical perforation I91 to permit the passage of air from the diaphragm valve. The conical projection of the circular metal member I95 provides for surface engagement to by means of the engaging screw threads '2 and which is perforated centrally at 206 to permit the free operation of rod I11,

It should be noted that bearings are provided for rod I11 by the perforations within the bus bar and in the metal stop 203. The biasingmeans for rod I11 is obtained by springs acting between the metal disk 202 and stationary members. Thus a small diameter central spring 206 bears against both the inner face of disk 202 and the inner face of the metal stop 203. This spring is of relatively small diameter and fits over the rod I11 which thus acts as a guide therefor.

I the closed circuit position.

A second and adjustable spring 201 bears against the inner face of the disk 202 and also against a movable or adjustable guide 2i I. The guide 2 is a ring shaped metallic member having a perforation 2I2 of diameter large enough to pass over the spring 206 but small enough to provide a seat for the end of th spring 201. The ring 2i I is slidably fitted within the hollow cylindrical member I93 and is adjusted therein by means of a plurality of fins 2I3 which project through axial slots 2 in the walls of the cylindrical member 3.

These fins may comprise merely two pins which have been embedded in the ring shaped member 2 and project from the axial slots 2 I4. As both spring 206 and spring 201 are continuously under compression, there will be a tendency to move disk 202 and its attached rod I11 to the right as viewed inFigure 1. The magnitude of this tendency is controllable by means of the adjustable nature of spring 201. That is, by threading the outer surface 2I5 of the hollow cylindrical member I93 and. passing a nut 2I6 thereover and in engagement with the threads 2I5, the fins 2| 3' the biasing force of rod I 11 and its associated magnetic armature I16. As,will be indicated in the following, the magnet I16 when operated,

controls the operation ofcontacts 3| and 32. Accordingly, an adjustment of either the air gap or restraining force on the armature I16 will correspondingly vary the magnetic forces required to displace the same and thus operate the circuit breaker. the tripping current required.

Two smallrcontrol switches are actuated by the rods I63 and I11. The switches as more clearly indicated in Figure 2 are mounted upon insulating brackets such as 2I1 and 2I8. The switches operable by their contact carrying rods are essentially butt contact switches employing a metallic bridge to complete the circuit between the two contacts. Thus as indicated in Figure 2, the rod I63 carries the bridging metallic member 22I which is engageable with the two butt contacts 222 .and 223.

The rod I63 passes through a perforation 22 within an insulating member 225 and thus i: maintained in slidable relation therewith. Th1 entire switch is clamped to the insulating bracke- 2" by means of the screws and bolts 226,

When the circuit breaker contacts 3| and 31 are closed, switch I63 is in the open circuit posi. tion. 0n the other hand, when rod I11 is biaser so that valve seat material comes into contac' with the metallic insert I95, the switch 23I is ll.

When contacts 3| and 32 are closed, curren flows from the bus bar or other electrical connection 235 which'is bolted to the line termina 11 but bymeans of the bolts 236 through thI engaged contacts and then-through the fiexibli conductor I24 to the tines of the bifurcated member I33, then through the magnet bus bar I11 am out through the cable or bus bar I35 fastenev thereto.

Under closed circuit conditions and no electri cal disturbances, the full tank pressure will axis in the passage 45 and the annular cored chambe 41 on one side of the diaphragm valve 46 ant also 'in'the chamber between the valve 46 am This then provides an adjustment for the dome shaped member 56. Under these conditions of equalized unit pressure on both sides, the valve 46 will be displaced more to the right as viewed in Figure 1 inasmuch as the left side of the valve has a considerably larger area than the ring-shaped under side of the valve. Therefore, with equal unit pressures on both sides of the diaphragm, the valve seat material 54 will be forced into engagement with the end of the projecting passage 52 and thus cut off the supply of air to the involute passage surrounding the contacts.

The contacts 3I and 32 are maintained in engagement allowing full air pressure to be established within the chamber 236 which will thus actuate piston I44 and rod I2I in a direction which will close the contacts against the action of the biasing compression spring I64.

However, the removal of valve disk 54 from contact with the projecting pipe 53 will allow full pressure to be built up in the involute passage 52 to the contacts 3| and 32.

From Figures 1 and 3, it may be seen that piston II4 which is fixed relative to cont-act 3I is of considerably larger diameter than the piston I43 and therefore without necessarily releasing the pressure in the chamber 236, the contact 3| will be displaced to the left as viewed in Figure l.

Full tank pressure is maintained in the chamber 236 by means of the closing manifold 231 which connects the air from the storage tank to each of the single pole circuit breakers controlled therefrom. The manifold 231 itself may comprise a Bakelite tubing perforated at 24I to allow the admission of air to and from chambe! 236 and the entire manifold as indicated in Figure 3 is supported between two clamping brackets 242 and 243 which are maintained in fixed relation by means of the plurality of bolts 244 which, in addition, fasten the brackets to the frame of the circuit breaker.

The nature of the manifold mounting is indicated in Figure 9 which is an end view of the I circuit breaker. The clamping action is secured by means of the bolts 244 as previously mentioned which pass through suitable lugs cast into the clamping bracket 242. 1

The semi-cy1indrical depression 245 in the clamp 243 which surrounds the air passage 24I which has been cut into the manifold 231 must be lined with a suitable gasket 246 to prevent leakage therefrom.

The clamping bracket 243 must, in addition to the semi-cylindrical depression 245, contain a perforation 241 which will allow the entrance of air to the chamber 236. Again, to prevent air leakage, the surface contact between the clamping bracket 243 and the hollow cylindrical member I4I must be sealed with a suitable gasket 25!.

The blast valve control manifold 255 is supported by means of a semi-cylindrical clamp 256 upon a boss 251 integrally formed on the dome shaped member 56. The boss 251 has been machined to accommodate the cylindrical manifold 255 which is rigidly clamped thereto by means of the plurality of bolts 26I which pass through suitable perforations in both the clamp and the dome shaped member. The manifold 255 comprises a Bakelite or other suitable insulating tubing which is interconnected with each of the poles of the circuit breaker as will be pointed out in the following discussion. I

To prevent leakage of air around the Junetion of the Bakelite manifold and the semi-cylindrical cut away in the boss 251, the semi-cylindrical opening is lined with a rubber or other flexible gasket 262 as is more clearly illustrated in the enlarged fragmentary view of the tripping manifold Figure 6.

The tripping manifold 255 is connected by air passages to the control diaphragm valve 46 and the valve 26I which is operated by the electro magnetic device I16. A perforation 263 in the tripping manifold is connected by means of the duct 264 to the nozzle I91, formed in the metallic disk I95, which forms the seat for the valve disk 2M.

The cylindrical opening I91 and the conical tapering opening I96 have, in addition, been joined to the inner portion of the dome shaped member 56 by means of a circular array of holes 265 and thus duct 264 is effectively interconnected with the space between the dome shaped member 56 and the diaphragm valve 46, whether the valve 20I is open or closed. The portion of duct 264 projecting into the nozzle shaped opening in disk I95 has been designed so that an aspirating effect is secured when air flows through duct 264 and through opening I91, to draw th air through holes 265 when valve 2! is opened.

An additional air passage is provided from the manifold to the dome space by means of a duct 266, more clearly illustrated in Figure 6, and the flow of air through this duct is controlled by a check valve 261 formed in the rubber gasket 262. As seen in Figure 5, this duct is displaced sideways from duct 264. The duct 266 leads into the manifold 255 through a rectangular or other relatively large perforation 21I which has been formed therein. It should be noted from Figure 6 that the perforation 2II is relatively large when compared to the duct 266.

This valve is formed by cutting two parallel slits 212 into the gasket on either side of the duct 266 as indicated in the fragmentary view of Figure '1.

The diameter of the larger perforation 21I in the manifold is greater than that of the spacing between the two slits. Therefore, when the pressure in the manifold 255 is low, as compared with the pressure of the air within the dome, there will be a tendency for the air to flow, as indicated by the arrow heads in Figure 6, in a manner such that the flexible material contained between the slits 212 will bend as indicated and thus allow air to pass around the slits and into the manifold.

On the other hand, if the pressure in the manifold 255 is greater than the pressure within the dome, there will be a tendency to force the flexible material, between the slits, up against the smaller duct 266 and thus effectively check the flow of air through the duct. The reasons for this arrangement will be taken up in the follow paragraphs.

When the circuit breaker is connected in circuit with the anodes of the rectifier as in Figure 15, and all the poles are closed, the individual poles are interconnected by the manifolds 231, and 255, and the full tank pressure will exist in both manifolds. Therefore, as a full tank pressure also exists in the passage 45 and in the annular chamber 41, the diaphragm 46 will be moved as determined by the side having the greater surface area.

This obviously is the side which is adjacent the dome shaped member 56 as the area of the valve disk covering the blast pipe is at atmospheric pressure. Full tank pressure exists be- 3 between contacts 3i and 32 bar I13 and therefore tween diaphragm l6 and the inner wall of the member 36 inasmuch as this chamber is connected with the tripping manifold 255 through the duct :64 and the plurality of perforations 265. It should be recalled that for normal conditions of operation (that is, values of current up to the current for which the armature is ad- Justed), that the valve 2III is normally biased to engagement with the disk I95 and therefore the air within the dome and within the tripping manifold does not escape. Should a fault occur on the anode to which the pole under discussion is connected, the armature to the left as viewed in Figure 1 under the influence of magnet I12, and the valve 20I will be removed from surface engagement with the disk I95.

This will immediately allow the air contained within the dome to exhaust through the plurality of openings 2 and through the nozzle shaped opening I91. This air will pass to the outer' atmosphere through the guide fins around the valve 2IlI and then through the perforations 2 I4 within the wall of the hollow cylindrical member I93.

In addition to this escape air which is flowing through opening I91, air will flow from the tripping manifold through the duct 264 and out through the opening I91. Inasmuch as this outflowing air is at a high pressure, means must 'be provided to prevent it from reducing the velocity flow from the dome through this passage.

The aspirating effect has been arranged in order to increase the velocity of the air flowing from the dome. High pressure air cannot enter the dome through the duct 266 because the check valve 261 effectively blocks any such flow.

A reduction in pressure within the dome will immediately allow the full air pressure contained within the chamber 41 to actuate diaphragm valve 46 to the left as indicated in Figure 1 and accordingly allow the main jair blast entering from the tank, upon which the breaker is mounted, to flow into the involute assage 2. The in- I16 would be actuated ly completing the circuit crease in pressure withinthe passage 82 will operate upon the relatively large diameter piston H4 and will .thus force contact 3I to the left against the action of the high pressure air upon the small diameter'piston I43. Immediately thereafter an arc will. be drawn which will be extinguished by means of the high velocity air blast which is in this instance air blast.

The heated air will exhaust through the nozzle shaped contact 32 and its associated extension 8|. Upon flowing through the muiller '2, the air stream will be cooled by the'stack II3 which as previously described,'comprises a parallel stack of spaced metal plates. During the operation of the circuit breaker under the influence ofan overload or fault current two other important operations are performed in the following sequence. First, upon the actuation of magnet armature I16, the switch 23I is opened, and second, immediately following the'displacement of contact 3i contacts of switch 221 are cl The position of the armature I16 is determined by the current flowing through the magnet bus immediately following current interruption, the force upon armature I16 will vanish and therefore the armature I16 will again be solely under the" influence of the biasing springs 208 and 201.

The springs will carry the valve disk 2M into to the left, the

a rotatingor spinnin! 3 engagement with the metallic member I95. It is important to note that the springs 206 and 201 must supply sufficient biasing force to close the valve although full tank pressure exists within the opening I91. The reclosure of valve 2M will, through ducts 264, and the plurality of openings 2, cause the pressure to the rear of diaphragm 46 to build up to the full tank pressure whereupon the diaphragm valve will immediately close and thus cut off the supply of air flowing through the involute passage 52. w

This precaution has been taken, to preclude the possibility of the air stored within the tank from completely discharging through the chamber 52 and its associated exhaust passages. Again, assuming that no other external influences have acted upon the circuit breaker, the removal of the air supply from chamber 52 will effectively decrease the pressure therein and accordingly if the full pressure still exists within the closing manifold 231, air will flow to operate the piston I43 and its associated piston rod I to the right asviewed in Figure 1 to close contacts 3| and 32 and thus complete the circuit which has been interrupted by meansof the automatic electromagnetic tripping device I12.

The cycle of events described immediately above concerning the operation of the circuit breaker under the influence of an overload as sumed that the pressures 231 and 23! remained at the storage tank value,

The nature of the changes occurring in the pneumatically operated control system will now be described with reference to the operation of a sries of single pole circuit breakers, each of which is in circuit with an anode of a mercury arc rectifier. l a

The complete control system for a circuit breaker of which Figure 1 is a typical. example, comprises means for manually and automaticalto all of the anodes simultaneously. In addition, it contains a plurality of protective features such as under pressure tripping mechanism and may be arranged so that each circuit breaker may through a counting system=open and reclose a predetermined number of times prior to the opening of all the poles of the circuit breaker.

, The control system schematically illustrated in Figure 12 shows a plurality of poles such as those of Figure 1 insulatedly mounted upon a main storage tank3III which is illustrated in elevation and'g in section. This storage tank is maintained at a pressure within predetermined limits by means of an air compressor.

The six single pole circuit breakers, which have been schematically represented, are indicated by the numerals 302-331 but to facilitate the following description of the operation of the controlling system, a diagrammatic representation of the pole of Figure 1. I

In carrying over the reference numerals applied in Figure 1 the current enters the pole 301 through the bus bar 235 which is joined to the contact 32 mounted upon an insulator IIII within the main casting '38. Cooperating contact 3I is mounted upon a piston I II which is in turn in operative relation with smaller diameter piston I43 through rod I2I. From contact 3I the current is carried by the flexible conductor I24, by bar I13 through the horse-shoe" magnet I12, and thustothe bus bar I33. j

The armature I13 is in operative relation with the magnet I12 and is carried pon theplunger in the two manifolds the pole 301 has been drawn to be rod I" which in turn carries the valve 20 The diaphragm valve 45 controls the air stream entering through chamber 45 to passage 52 which surrounds the contacts. The tripping manifold 255 communicates with each of the domes formed between member 55 and the diaphragm 46; and the closing manifold 231 communicates with each of the closing cylinders and associated piston The switches 221 and 23| are operated by the plunger rods |2| of the breaker contact and I" of the armature respectively. The circuit breaker 301 is illustrated as tripped and having been caused to remain open. However, it should be noted that the valve 20| has been closed and that therefore diaphragm 45 has been displaced under the influence of air entering" the dome from the manifold 255 to shut off the blast air.

Air is supplied to the tripping manifold 255 through a tap 3 from the main storage tank through an electromagnetically operated valve the dome shaped member 55 and the diaphragm valve 43. However, when in the deenergized position, the schematically represented plunger 324 will be actuated by the spring 325 to allow the high pressure air within the tripping manifold 255 to exhaust through the indentation 325 contained therein. The operation of solenoid 3|5 will not permit the escape of air through the coupling 321 within the valve and thus will not permit the escape of air stored within the tank.

The closing manifold 231 utilizes the compressed air of the storage tank 3M taken at the tap 3| I through pipe 33|. An electromagnetically operated valve 332 controls the'influx of air thereto and when the solenoid 330 is in the deenergized position as indicated in Figure 12, the

' air contained within the closing manifold 231 is 3|2. The members 3|3 at each of thepoles repa resent the junction between the manifold 255 and the diaphragm valve 45 of each of the poles. The control system is electrically operated from a direct current source which may be copper-oxide rectiflers, batteries or the like, and has been schematically illustrated by the battery 3| 4.

The valve 3|2 is controllable by means of the electromagnetic device which in Figure 12 is schematically illustrated as a plunger type solenoid 3|5 which in the circuit indicated is op rated by two parallel switching and control systems. One of these control lines originates at the negative control bus bar and contains in series therewith the plurality of switches 221 each of which is operated by the piston rod |2| of its associated circuit breaker.v

From the plurality of serie switches 221, the

electrical circuit then passes through relay 3|6 and solenoid 3| 5 and then terminates at the positive bus bar. A second circuit also originates at the negative control bus bar and then contains three switches in series: switch 32| which is the hand trip, switch 322 which is the underpressure automatic trip, and switch 323 which is an interlocking switch. These three switches and their specific functions will be described in later paragraphs. v

In series with these three switches are the plurality of switches 23| one of which is mounted upon each of the circuit breakers. At the termination of these switches, the control line extends to the positive bus through the relay 3|5 and the solenoid 3 5.

There are, therefore, two parallel circuits for controlling the relay 3| 6 and the solenoid 3| 5, and either circuit will be effective for the energization thereof. v

Each circuit comprises a plurality of switches in series. Therefore, if one or more switches in each of these circuits are opened, the relay and solenoid will be deenergized. When all of the circuit breakers are closed, the corresponding switches 221 are all in their open position and the control of the relay and solenoid depends solepermitted to escape through the piping connection 333 and the indentation 334 within the solenoid plunger 335.

The spring 335 is employed to depress the solenoid plunger 335 when the electromagnetic device is deenergized. In the energized position, the perforation 34| within the solenoid plunger permits the flow of air from the tank 3M to the closing manifold 231.

Joined to the closing manifold is a relief valve 342 which may be employed to vent the closing manifold. When this valve is open, accidental closing of the circuit breaker contacts is impossible.

It is to be recalled from the construction of the single element of the circuit breaker a indicated in Figure 1, that the switching member 221 is open circuited when the contacts 3| and 32 are in engagement and the switching element 23| contained on each of these elements are in the closed circuit position during normal conditions.

Therefore, when the circuit breaker is in the closed circuit position, the switches 221 do not control the operation of the electromagnetic device 3l5. If normal condition prevail, the switches 23| and the switches 32|, 322 and 323 will all be closed and the electromagnetic device 3|5 will be energized and the plunger 324 will be in the position indicated in Figure 12. This allows air pressure to be built up within the tripping manifold 255 which closes the diaphragm valve 45 to prevent the flow of air into the involute chamber 52.

This condition, of course, prevails in each of the individual circuit breaker poles 302-301. If any one of the switches 32I, 322 or 323 are opened for reasons which will hereinafter be described, the electromagnetic device 3 l5 will be deenergized and vent the tripping manifold 255 to cause the ly upon the normally closed switches in the other permits the entry of air into the space between opening of all the diaphragm by virtue of the pressure drop within the dome.

When the tripping manifold is vented by the deenergization of solenoid 3|5, air flows from the dome through the manifold and to the atmosphere through the passage 264. The check valve in the tripping manifold 254 assist in the release of the dome pressure since it permits the flow of air from the dome through relatively short passage 255 (as illustrated in Figure 6) to the manifold. The check valve, therefore, functions to accelerate circuit interruption accomplished by the opening of switches 32 |-323.

Energization of any one of the trip magnets will cause valve 2|l| instantaneously to vent its associated dome and cause the main contacts of the breaker to separate. Since valve 20| is mechanically interconnected with switch 23|, displacement. thereof, to Vent the dome will cause deenergization "bf solenoid 3l5, venting of trip manifold 255, and subsequent opening of all the other poles of the circuit breaker.

It is desirable to reenergize the electromagnetic device 3!5 immediately after circuit interruptions so that the valve diaphragm 43 may reclose and preclude the exhaustion of the air within the storage tank 30 If tripping occurs due to overcurrent on one of the poles (or reverse current, when a polarizing magnet coil is employed), and thus due to a movement of one of the switches 23!, reenergization of the electromagnetic device 3!5 will occur immediately after current interruption, since the compression springs acting upon the armature will close switch 23! of the initiating pole, and complete the energizing circuit of the solenoid.

However, if circuit interruption i a result of operation or one of the three switches 32!, 322 and 323, it is necessary to provide other means for reenergizing electromagnetic device 3!5 in order to reclose the diaphragm valves 48 to preclude the escape of the entire charge of the storage tank. These means will be described subsequent to the description of the switche 32!, 322

and 323.

Inasmuch as the circuit into which these three switches are connected controls the tripping of the circuit breakers, these switches-are utilized to provide manual and other types of automatically operating systems, as follows:

Switch 32! is a normally closed manually operated push button. It provides for a hand trip whenever it is necessary to shut down the rectifier or other apparatus connected thereto.

Switch 322 is controlled by a pressure gauge trol line maybe open. This reenergization will result in the closure of diaphragm valves 45.

Manual closing of the circuit breaker is accomplished by the operation of the normally open switch 35!. This switch through the agency of relay 35'! controls the solenoid 333 of the air valve 332 in the closing manifold. The energization of electromagnetic device'33ll will, as previously mentioned, permit the influx of high pressure air through valve 332 to the closing cylinders and their associated pistons which will move the contacts 3| and 32 into engagement.

A second switch 352 with normally closed contacts is in series with switch 35 and opens when mounted upon the storage tank. Thus if the 1 pressure within this tank falls to the minimum 'value required for eilective and rapid circuit trol line comprising the three above described switches and the switches 23! which are mounted upon individual circuit breaker elements, in order that other devices within the system may control the operation of the anode circuit, if necessary.

the air pressure in tank 30! is below a safe value for closing the breaker on a fault. As will be seen, the cycle of events required for manual closing will be impossible when the contacts of switch 352 are open. v

. The relay 35! comprises an armature 353 normally biased to a mid-position between two magnet poles (not shown) which are energized by the coils 353 and 354. The contacts 38! and 353 are normally open and moved to a closed position by the armature when it moves upward, toward the magnet pole of coil 354.

The coil 354 is magnetically stronger than coil 353 so that when the coils are energized simultaneously by the closure of switch 35!, the upper coil predominates and the contacts close. The

contact 35! short circuits the switch 35!, so that after operation it may be released without deenergizing the relay. The contact 353 completes the circuit to the solenoid 330 of the solenoid of the closing valve. v

The circuit of coil 353, when the relayis energized, is from the negative control bus, through the switches 35! and 35!, in parallel and through coil 353 to the positive control bus- The circuit of the cell 354 is from the common terminal of coils 353 and 354, through the coil, through con- Since these three switches may operate and remain in their open circuit position, it is necessary as previously mentioned toprovide means operative to reclose diaphragm valves 45 so that the compressed air within the tank may not be exhausted.

This is accomplished by the series of interconnected switches 22'! actuated by the piston rod !2! of the contact 3!. Accordingly, following circuit interruption due to a disturbance within the control line containing the switches 23!, and 32!, 322 and 323, contact 3| and its associated piston rod !2! will be displaced to'the left as viewed in Figure 12 andthe arc extinguished. Upon the completion of the displacement of all of the pistons, ,contacts'.22! will close and reenergize the electromagnetic device 3!5, although one of the switches in the parallel contact 355 of auxiliary relay 3! 5 provided that relay 3!5 is energized, to the negative bus. Relay coil 3!5 as hereinabove described, is energized whenever the electromagnetic device 3!5 is energized through either of the parallel circuits previously described. j

The relay armature 358 has two diflerent actions at deenergization depending upon the position of switch 35!. Thus, if switch 35! is open,

the separation of contacts 355 deenergizes cell 354 and permits the contacts 35! and 353 to part. deenergizing coil 353 and allowing the armature to return to its normal mid-position. If the switch 35! is held in the closed position and the contacts 355 separate, the coil 354 is deenergized, but the cell 353 remains in circuit. The relay armature 353 is therefore drawn down beyond its normal mid-position against the magnetic pole of coil 353 and held in that position with contacts 33! and 333 open. If; during this condition, the contacts 355 of relay 3 i5 reclose, the contacts 35! and 333 will remain open despite thereenergiza-v tion of coil 354.- When the switch 35! is released, the coil 353 will be deenergized and the armature will return to its normal mid-position.

The relay 3l3 provides an interlock between the tripping system and the solenoid 33!! controlling the air pressure in the closing manifold. When the breaker is tripped, the closing manifold must be disconnected from the storage tank and vented to the atmosphere to prevent reclosure of the breaker contacts when the blast valve diaphragms close, The coil of this interlock relay m is, there- I circuit breaker.

with the coil 3!! of the 3!2 so that they are defore, connected in series tripping manifold valve energized simultaneously upon the automatic opening of any breaker pole. This action vents the trip manifold 255 for actuation of all the unoperated blast valve diaphragms, and at the same time, by the separation of contacts 355 de- Upon the opening of all the circuit breaker poles, a control circuit will be established through the switches 221 to reenergize coil 315 and close all the blast valves, which as previousl described, will preclude the exhaustion of the storage tank. This action will simultaneously energize relay H3 and close contacts 355. Under this condition, as previously described, the relay 351 cannot reclose its contacts 35! and 333 no matter whether the control switch 35! is open or closed. This effectively prevents repeated opening and closing of the breaker contacts when the switch 35! is closed during a fault condition.

As the control system requires that full air pressure be maintained on the closing manifold when the breaker contacts are in closed position, the coils 353 and353 of relay 351 and coil 333 of the air valve are designed for continuous duty.

This condition is also true of the tripping system as the coils 3!5 and 3" are deenergized only during opening movement of the breaker contacts.

It is frequently possible and desirable in the operation of certain polyphase circuits, to permit the interruption and immediate reclosure of a single pole of the circuit breaker without necessariiy interrupting the other poles thereof. More particularly, it has been rectifier faults such as backfires may be cleared by merely opening and reclosing the affected anode circuit, while permitting normal operation of the unaffected anodes.

In order to provide for such an arrangement within the control system illustrated in Figure 12, it is necessary to preclude the operation of one of the switches '23! immediately upon the occurrence of an overload. Yet it is necessa y to actuate switch 23! to interrupt all of the poles if the anode fault is permanent in that it cannot be removed unless the mercury arc rectifier is shut down and repaired.

Figure 14 illustrates one modification of a device which may be mounted upon the circuit breaker illustrated, which functions to permit a single pole to open and reclose several times before the entire mercury arc rectifier is taken out of operation.

In order to modify the circuit breaker in accordance-with Figure 14, it is necessary to remove each of the switches 23! from its fixed ,relation with shaft I11, which carries the armatrue !13 of the electromagnet !12.

Attached to the end of the shaft I11 in place of the switch 23! is a pawl 31! biased by means of spring 312 into engagement with a ratchet 313. In addition, the locking cooperation with ratchet 313 vby means of spring 313 which may be pinned to the frame of the The occurrence of an overload will displace shaft I11 to the left as in conjunction with the pawl 31! and the locking device 315 will rotate the ratchet 313 through an angle as determined by a single notch .thereon.

found that internal.

Viewed in Figure 14 and s device 313 is biased into i tion of the circuit breaker pole A lever 313 which is fastened to the ratchet by means of the screw 311 is positioned to operate a switch 33! which occupies the same position as switch 23! in the control circuit of Figure 12. Therefore, a number of operations of shaft I11 due to repeated circuit overloads will continuously rotate ratchet 313 until lever arm 315' opens switch 33! to open circuit all of the circuit breaker poles in a manner described in connection with the operation of switch 23!.

A single overload occurring in one of the poles will move the ratchet one notch, vent the dome behind the diaphragm to open the single breaker, and due to the biasing action of the springs about shaft I11, the circuit breaker pole in which the fault occurred will reclose immediately following circuit interruption.

The number of successive interruptions which may be allowed before all of the poles are interrupted may be predetermined by suitably positioning the lever arm 313.

The system as indicated in Figure 14, provides a number of cycles prior to the interruption of the entire mercury arc rectifiers anode circuits and is cumulative in its operation, that is, if several cycles of opening and immediate reclosing are required to clear an internal rectifier backfire, and if similar backfires occur later in the operation of the rectifier, the ratchet 313 will again progress several notches and thus after several backfires or several instantaneous circuit interruptions, the ratchet will have progressed suillciently to actuate the switch 33! and interrupt all of the circuit breaker poles. Thus, an anode which is frequently giving trouble will eventually cause the rectifier'to be shut down.

In the above device, subsequent to the interruption of all of the circuit breaker poles, it is necessary to readjust or reorient the ratchet 313 in order to reset lever 313to its original position. In order to overcome this inconvenience, the modification illustrated in Figure 13 may be employed.

In this modification, each of the switches 23! are in circuit with a solenoid 332 through a parallel circuit of an annunciator 333 and an electrically operated counter 333.

In this modification, the switches 23! have been removed from the control circuit in series with the tripping solenoid H5 and have all been replaced by a single switch 33! which is in operative relation with the solenoid plunger 335, through a notching mechanism as will now be explained.

This series circuit is connected across the ten minals of a, direct current control circuit such as the battery 3!3 of Figure 12, and thus following the actuation or, any of the switches 23!, the solenoid plunger viewed in Figure 13.

The closure of one of the switches 23! will actuate the lever 333 of the annunciator about its pivot 331 to release the flag or other resettable visual indication 333 which an indicawhich has been operated. This visual indicator may be of the type which can only be reset manually. The operation of one of the switches 23! will correspondingly operate the associated counter 333 to provide some indication of the number of faults which occur in the particular anode circuit.

The closure of any switch 23! will operate the plunger 335 upwards as viewed in will in turn cause rotation of shaft 333. Rotatably mounted upon 335 will operate upwardly as I Figure 13 which 399 is a ratchet wheel 394 which carries lever arm 39! in fixed relation thereto. A pawl 399 which is pivotally mounted upon the lever arm' A biasingspring 39! tends to rotate ratchet 393 in a direction opposite to that obtained by an upward displacement of plunger 385, and normallypulls lever 395 against a fixed stop 399.

A locking device 40l pivotally mounted upon the pin 402 is biased in the direction required for engagement with ratchet 394 and when in engagement therewith will prevent spring 391 from rotating the ratchet. However, locking device 40! is normally" disengaged from ratchet 394 by means of the gravitational eifect of a piston 403 and piston rod 404.

Piston rod 494 is in alignment with plunger rod 385 and its associated piston 403 is slidably fitted within a cylinder 405 which is vented through an adjustable exhaust 406. During normal operation of the circuit breaker anodes, the solenoid 382 is deenergized and thus the locking device piston and ratchet assume the positions indicated in Figure 13, wherein it may be seen that the pawl 396 engages a stop 409 which causes disengagement from ratchet wheel 394 and ermits spring 391 to rotatethe lever 995 against its stop 399.

Energization of coil 382 due to the closure of one of the switches 23l will rapidly raise plunger 385 and thus rotate ratchet'394 through one or more notches. In addition, the operation of plunger rod 385 will drive piston 403 up into the cylinder 405 and thus allow locking device 40| to come into engagement with ratchet 394 to preclude restoration to its original position immediately upon the deenergization of coil .382. Therefore, member 395 will remain in a substantially fixed position until piston 403 and its associated piston rod 404 descend and disengage the locking device 40l from the ratchet 394.

The adjustable small exhaust 400 provides in effect, when combined with the cylinder and piston a time delay mechanism inasmuch as the descent of piston 403 will be relatively slow. As the circuit breaker operation is similar to that previouslydescribed, the anode pole which has been opened due to a fault will immediately re If the circuit breaker is operating upon a permanent rectifier fault, a succession of operations will be required before switch 39l is opened to isolate the rectifier from the transformer secondaries.

Subsequent to the interruption, the piston 403 will descend and free the ratchet from the locking device to permit spring 391 to return the ratchet to its original position.

The entire system as illustrated in Figure 13, will therefore serve as a counting mechanism in order that any of the anodes be allowed to operate several times before the mercury arc rec tifier is isolatedfrom the line. In addition, it serves to visually indicate upon which anode the fault has occurred and the total number of operations of each pole of the circuit breaker.

It is important to note that the systems illustrated in Figures 12, 13 and 14 are entirely schc-' matic, that the valves, solenoids, relays, time delay mechanisms and the like have been illustrated in their simplest form merely to facilitate the explanation of the system involved.

The various relays and'other devices required may be of the known commercial types and need only function as the devices illustrated in order that they may be applied to the control circuits.

It will be evident that many modifications of the above-described circuit breaker design and circuit breaker control systems may be made-by those skilled in the art and therefore I do not wish to be limited to the specific disclosures hereinabove set forth. but only by the scope of the appended claims.

This is a division of my application Serial No. 371,092, filed December 21, 1940, entitled Air blast circuit breaker and control therefor.

I claim;

1. In electrical switching apparatus for a plurality of circuits, individual circuit breaker elements in each of said circuits, a source of high pressure fiuid, means including said fluid for causing the simultaneous engagement of the contacts of each of said elements, means including said fluid for causing the simultaneous disengagement of said contacts, and automatic means on each of said breakers for disengaging its conclose. If the fault is still present within the circuit, the switch 23! will be reclosed immediately and will again actuate plunger rod 385 to again rotate ratchet 394 through one or more notches. And inasmuch as piston 403 has not completed its descent, the locking device 40l will again preclude the return of the ratchet to its original position.

Therefore, it may be seen that repeated operations of the circuit breaker contacts will cause a continued rotation of ratchet 394 and at the termination of the predetermined number of cycles, the member 395 will open switch 39i which, as previously mentioned, is. in the control circuit and will interrupt all of the circuit breaker I poles.

is in. the deenergized position.

associated circuit breaker tacts independently of the contacts of itsassociated breakers.

taneous disengagement of the contacts of the' associated circuit breaker element, and means controlled by the operation of said single pole breaker for causing the contacts of all of said rectifier.

3. In electrical switching apparatus for a polyphase mercury arc rectifier, individual circuit breaker elements in each automatic means operative upon the occurrence of a fault in an anode circuit for instantaneously separating and reengaging the contacts of the element, said contacts remaining in .said engaged position if said fault is cleared, and opening and 'reclosing repeated- 1y if said' fault remains, andmeans for disengaging the contacts of all of said breakers when disengagement of the elements to isolate said said contacts have opened and declosed a predetermined number of times, said last mentioned anode circuit thereof, 

